Chimney channel (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">chimney channel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for flue that I've seen before include "Passage for air" , "Chimney pipe to draw off smoke" , "Chimney channel" , "Chimney passage" , "smoky passage" .)